A Surface Site Interaction Point Method for Dissipative Particle Dynamics Parametrization: Application to Alkyl Ethoxylate Surfactant Self-Assembly

Abstract

Dissipative particle dynamics (DPD) is a coarse-grained approach to the simulation of large supramolecular systems, but one limitation has been that the parameters required to describe the noncovalent interactions between beads are not readily accessible. A first-principles computational method has been developed so that bead interaction parameters can be calculated directly from ab initio gas-phase molecular electrostatic potential surfaces of the molecular fragments that represent the beads. A footprinting algorithm converts the molecular electrostatic potential surfaces into a discrete set of surface site interaction points (SSIPs), and these SSIPs are used in the SSIMPLE (surface site interaction model for the properties of liquids at equilibrium) algorithm to calculate the free energies of transfer of one bead into a solution of any other bead. The bead transfer free energies are then converted into the required DPD interaction parameters for all pairwise combinations of different beads. The reliability of the parameters was demonstrated using DPD simulations of a range of alkyl ethoxylate surfactants. The simulations reproduce the experimentally determined values of the critical micelle concentration and mean aggregation number well for all 22 surfactants studied.

Systematic Parameterization of Ion–Surfactant Interactions in Dissipative Particle Dynamics Using Setschenow Coefficients

“…For this work, we use a recent DPD force field which has been extensively validated for surfactant simulations. 47 , 48 …”

Translation of Chemical Structure into Dissipative Particle Dynamics Parameters for Simulation of Surfactant Self-Assembly

“…CMC values were collected after 5.0 × 10 5 timesteps for all systems. As previously reported, 14 the value of N cut used to discriminate between premicelles and stable micelles was obtained from the aggregation number distribution P ( N ). For highly soluble surfactants, N cut is identified as a local minimum in the P ( N ) distribution, while there is usually a clear gap between the two populations for less soluble surfactants.…”

“… 18 , 19 A number of different approaches to deriving a ij repulsion parameters have been described using experimental or calculated transfer free energies. 14 , 18 − 20 Groot and Warren matched the equilibrium distance with the maximum in the radial distribution function to develop a soft sphere model for linear polymers ( a ij = 25 and ρ = 3). 20 Since then, it has become common practice to choose values depending on the situation requirements.…”

Using Dissipative Particle Dynamics to Model Effects of Chemical Reactions Occurring within Hydrogels

“…Hence, the aqueous solution is a strongly unfavorable solvent for the beads that have formed a complex; in other words, the interaction between the solution and bound beads becomes hydrophobic. The value we chose for a cs is comparable to effective repulsive parameters [31,32] extracted from a first-principles computational method, i.e., the "surface site interaction points" (SSIP) model. Here, the large a cs value is used to capture the interactions that lead to the collapse of the gel in the comparable experiments.…”